std::locale::operator()
From cppreference.com
| template< class CharT, class Traits, class Alloc > bool operator()( const std::basic_string<CharT,Traits,Alloc>& s1, |
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Compares two string arguments s1 and s2 according to the lexicographic comparison rules defined by this locale's std::collate<CharT> facet. This operator allows any locale object that has a collate facet to be used as a binary predicate in the standard algorithms (such as std::sort) and ordered containers (such as std::set).
Parameters
| s1 | - | the first string to compare |
| s2 | - | the second string to compare |
Return value
true if s1 is lexicographically less than s2, false otherwise.
Possible implementation
template<class CharT, class Traits, class Alloc> bool operator()(const std::basic_string<CharT,Traits,Alloc>& s1, const std::basic_string<CharT,Traits,Alloc>& s2) const { return std::use_facet<std::collate<CharT>>(*this).compare( s1.data(), s1.data() + s1.size(), s2.data(), s2.data() + s2.size()) < 0; } |
Example
A vector of strings can be sorted according to a non-default locale by using the locale object as comparator:
Run this code
#include <algorithm> #include <cassert> #include <locale> #include <string> #include <vector> int main() { std::vector<std::wstring> v = {L"жил", L"был", L"пёс"}; std::sort(v.begin(), v.end(), std::locale("ru_RU.UTF8")); assert(v[0] == L"был"); assert(v[1] == L"жил"); assert(v[2] == L"пёс"); }
See also
| defines lexicographical comparison and hashing of strings (class template) |